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[81.101.252.173]) by smtp.gmail.com with ESMTPSA id o19-20020a05600c379300b003b47b80cec3sm12379207wmr.42.2023.02.11.16.14.59 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 11 Feb 2023 16:14:59 -0800 (PST) Message-ID: <89f2f365-6592-9eac-4f90-05ce7477233f@jguk.org> Date: Sun, 12 Feb 2023 00:14:59 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.7.1 Subject: Re: build error --std=c++17 vs --std=c++23 -Wrestrict "may overlap up to 9223372036854775813 bytes at offset -3" From: Jonny Grant To: gcc-help References: <681c1224-aec4-9831-26b1-e11fd182dd5c@jguk.org> Content-Language: en-GB In-Reply-To: <681c1224-aec4-9831-26b1-e11fd182dd5c@jguk.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-4.0 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,KAM_SHORT,NICE_REPLY_A,RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS,TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: I saw there are quite a few similar issues reported. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=Wrestrict Maybe it is similar to this one https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105651 Jonny On 11/02/2023 23:38, Jonny Grant wrote: > Hello > > Anyone else seeing an issue when using c++23 ? > gcc (Ubuntu 12.2.0-3ubuntu1) 12.2.0 > > The only change is to use --std=c++23 > > -Wrestrict is enabled by -Wall > > > #include > > typedef struct a_bc > { > std::string a; > std::string b; > } a_t; > > void f() > { > a_t c; > > c.a = " sdfsdf fsdfsdf fdfsfdsdf "; // seems to need this long string to reproduce, down to 8 bytes it didn't > c.b = "E"; > } > > > > > > > > > $ g++ -O3 --std=c++23 -Wall -c -o gcc_err3 src/gcc_err3.cpp > In file included from /usr/include/c++/12/string:40, > from src/gcc_err3.cpp:4: > In static member function ‘static constexpr std::char_traits::char_type* std::char_traits::copy(char_type*, const char_type*, std::size_t)’, > inlined from ‘static constexpr void std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::_S_copy(_CharT*, const _CharT*, size_type) [with _CharT = char; _Traits = std::char_traits; _Alloc = std::allocator]’ at /usr/include/c++/12/bits/basic_string.h:423:21, > inlined from ‘constexpr std::__cxx11::basic_string<_CharT, _Traits, _Allocator>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::_M_replace(size_type, size_type, const _CharT*, size_type) [with _CharT = char; _Traits = std::char_traits; _Alloc = std::allocator]’ at /usr/include/c++/12/bits/basic_string.tcc:532:22, > inlined from ‘constexpr std::__cxx11::basic_string<_CharT, _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::assign(const _CharT*) [with _CharT = char; _Traits = std::char_traits; _Alloc = std::allocator]’ at /usr/include/c++/12/bits/basic_string.h:1647:19, > inlined from ‘constexpr std::__cxx11::basic_string<_CharT, _Traits, _Alloc>& std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::operator=(const _CharT*) [with _CharT = char; _Traits = std::char_traits; _Alloc = std::allocator]’ at /usr/include/c++/12/bits/basic_string.h:815:28, > inlined from ‘void f(const std::string&, bool, bool)’ at src/gcc_err3.cpp:17:13: > /usr/include/c++/12/bits/char_traits.h:431:56: warning: ‘void* __builtin_memcpy(void*, const void*, long unsigned int)’ accessing 9223372036854775810 or more bytes at offsets -4611686018427387902 and [-4611686018427387903, 4611686018427387904] may overlap up to 9223372036854775813 bytes at offset -3 [-Wrestrict] > 431 | return static_cast(__builtin_memcpy(__s1, __s2, __n)); > | ~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~